Electric furnace



Dec. 5,1925.

1,564,800 M. UNGER ELECTRIC FURNACE Fi led March 12, 1924 Inventor: M agnus Unger,

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ELETHEC FURNCE.

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To @ZZ whom t may com/cern l Be it known` that I, liAGNUs llerena, a citizen of the United States, residing at Pittsfield, in the county. of Berkshire, State lof Massachusetts,'have invented certain new and useful Improvements in Electric Fui naces, of which the following is a specification.

My invention relates to electric furnaces and has for its object the provision of improveniente therein whereby greater current densities can be used in the molten charge and the rapidity 'of heating thereby increased.

My invention relates more specically to electric furnaces of that type in which the charge is heated by means of a current passed through the charge. In electric furnaces of this type used in meltin metals there is a. tendency for the liquid c arge to be ruptured bythe so called pinch force which is incidental to the passage of electric current through any conductor. This pinch force has the eiiect of squeezing or constricting the conductor, and with a liquid conduc i tor will rupture the circuit if the current density becomes high enough. When rupture occurs the action of the furnace is intermittent and otherwise unsatisfactory so' that the maximum permissible current density in the current carrying charge for satisfactory operation is limited to that density which will produce ru turc. The power input and hence the rapi '.ty of heating is thus limited by the pinch force.

It is well known that by increasing the hydrostatic head of the molten charge, the pinch force is counteracted to some extent so that hi her current densities can be used whereby t e rapidity of heating may be increased. This hydrostatic head may be obtained by proviuing a deep narrow channel for the charge. A narrow channel has the disadvantage, hovrever, that it may not be satisfactorily recharged with pieces of the metal to be melted of' ordinary dimensions. To facilitate recharging a relatively Wide channel is therefore desirable, hut for rapid heating a deep, narrow channel is desirable.

In carrying out my invention use a relatively Wide channel provided with a deep narrow groove in the bottom whereby a hydrostatic head ofv metal may be produced to permit the use of higher current densities.

For a more complete understanding ot my invention reference shall be had` to the 'ac-- companying drawing, the single ligure oitv .which is an elevation view partly in section of an electric induction furnace my invention. l

Referringto the dran'ing'l have shown my invention in one form as embodied in an electric furnace of the inductiony type aithough it obviously hasapplica'tion to vari ous other furnaces in which the charge is heated hy current passed through the charge. This induction furnace comprises yan annular member l0, made of suitable refractorv material, provided with a horizontally' dis"- embodying posevd annular channel 11 for the charge 12.

The refractory member 10 is interlinlzed. by an iron core 13 on which is mounted a primary Winding 14. As' shown, the Winding 14 is concentrieally arranged with respect to the refractory channel member 10. It will be understood that thecharge 12 in the channel forms a closed secondary conductor for a transformer of which the coil lll is the primary winding.

In accordance'with my invention I provide a relatively rmueren' groove l15 in the refractory 10 at e bottom and forming a part of the 'channel 11. This` groove serves to increase the hydrostatic head of metal in the channel, that is, it increases its depth so as to counteractthe pinch force to some extent. It Will be observed that the groove, being relatively' narrow, does not materially increase the capacity of 'the channel, The eilect of the groove is particularly advantageous after a heat has been cured when only a small amount of metal is left in the channel. ln such case the hydrostatic head of molten metal due to the groove l5 permits the use of greater current densities inmelting the fresh charge thanwould be possible were this small amount of molten charge distributed lin a shallow pool over 'the relatively flat bottom of a wide channel. Also, it will be observed that with this arrangement the channel ll can be made any convenient Width to receive relatively large pieces in recharging and also to 'facilitate thc handling of slag.

lllhilc I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patentstatutes, it should he understood that l do not limit my loven-- 4tion thereto, since various' modifications all thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set rforth in the annexed claims.

What I claim as new and desire'to secure by Letters Patent of the United States is:

1. An electric furnace comprising a crucible providing a relatively Wide channel in which the charge is heated by current passed therethrough, said channel including a relatively deep narroT groove atthe bottom for increasing the hydrostatic head of molten metal` 2. An electric furnace comprising a crucible provided with a channel for the charge, said channel having a relatively Wide top portion, and a relatively deep narrow bottom portion for increasingithe hydrostatic headl of molten metal, and means for pro` ducing flow of-hcating current through the charge.

3. An electric induction furnace comprising a crucible providing a relatively Wide looped channel in 'which the charge constitutes a closed secondary, said channel including a relatively narrow groove at the bottom for increasing the hydrostatic head of molten metal.

4., An electric induction furnace compris ing a horizontally disposed annular crucihle providing a relatively Wide looped channel in which the charge forms a closed secondary, said channel including a relatively deep ,narrow groove at the bottom for increasing' the hydrostatic head of molten4 charge, a core interlinking said channel, and a primary winding on said core for inducing heating currents in said secondary.

An electric furnace for melting metals comprising a crucible providing a channel in which the charge is heated by a current passed through the charge, said channel heing relatively wide to receive large vpieces of metal to be melted and being provided with a relatively narrow groove at the bottom for increasing the hydrostatic head of molten metal without appreciably increasing the capacity of said channel.

In Witness whereof, I have hereunto set in v hand this eighth day of March, 1924.

MAGNUS UNGER. 

